digital_filter.h

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/******************************************************************************
 * Copyright 2017 The Apollo Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *****************************************************************************/

#pragma once

#include <deque>
#include <vector>

namespace apollo {
namespace common {

class DigitalFilter {
 public:
  DigitalFilter() = default;

  DigitalFilter(const std::vector<double> &denominators,
                const std::vector<double> &numerators);

  ~DigitalFilter() = default;

  double Filter(const double x_insert);
  void set_denominators(const std::vector<double> &denominators);

  void set_numerators(const std::vector<double> &numerators);

  void set_coefficients(const std::vector<double> &denominators,
                        const std::vector<double> &numerators);

  void set_dead_zone(const double deadzone);

  void reset_values();

  const std::vector<double> &denominators() const;

  const std::vector<double> &numerators() const;

  double dead_zone() const;

  const std::deque<double> &inputs_queue() const;

  const std::deque<double> &outputs_queue() const;

 private:
  double UpdateLast(const double input);

  double Compute(const std::deque<double> &values,
                 const std::vector<double> &coefficients,
                 const std::size_t coeff_start, const std::size_t coeff_end);

  // Front is latest, back is oldest.
  std::deque<double> x_values_;

  // Front is latest, back is oldest.
  std::deque<double> y_values_;

  // Coefficients with y values
  std::vector<double> denominators_;

  // Coefficients with x values
  std::vector<double> numerators_;

  // threshold of updating last-filtered value
  double dead_zone_ = 0.0;

  // last-filtered value
  double last_ = 0.0;
};

}  // namespace common
}  // namespace apollo